Transesterification of sunflower oil in microchannels with circular obstructions

The present paper studied numerical and experimentally the transesterification reaction between sunflower oil and ethanol with NaO H catalyst in microchannels with circular obstructions. The micromixer design influence on fluid mixing and oil conversion was investigated for a range of operating conditions: Reynolds number(Re = 0.1–100),Temperature(25–75 °C), ethanol/oil molar ratio(6-12), and catalyst concentration(0.75 wt%–1.25 wt%), using three microchannel configurations(Length = 35 mm; Width = 1500 μm; Height = 200 μm): T-shape – channel without obstructions; MCO – channel with 3 obstructions ensemble – equally disposed over longitudinal length;MWO – channel with 7 obstructions ensemble. The MCO micromixer was based on literature work, and the MWO is a totally new micromixer design. Experimental tests were conducted in similar conditions in microreactors using these micromixers(Length = 411 mm) made of polydimethylsiloxane. The MCO configuration presented the highest performance(mixing index of 0.80 at Re = 100), oil conversion of 81.13% at 75 °C, molar ratio of 9 and catalyst concentration of 1%. Experimental results showed high conversions for MCO and MWO configurations(99.99%) at 50 °C, molar ratio of 9 and catalyst concentration of 1%, with a residence time of 12 s.

Evaluation of Performance and Emission Characteristics of Biodiesel Fuel Produced from Rapeseed Oil

The objective of the present study is to examine and compare the performance and emission characteristic of two biodiesel fuels produced from rapeseed oil via transesterification method.Tested biodiesel fuels(ROME(Rapeseed Oil Methyl Ester)and ROEE(Rapeseed Oil Ethyl Ester))were selected based on their properties obtained from an optimization of transesterification conditions.A Yanmar diesel engine has led to evaluating their performance parameters such as fuel consumption rate,exhaust gas temperature and emission characteristic corresponding to nitrogen oxides(NOx),carbone monoxide(CO)and carbon dioxide(CO2).A comparative analysis was carried out using normal diesel fuel tested in same experimental conditions.Fuel consumption rate was measured by observing the volumetric rate from the fuel tank of the engine supported by stopwatch.The exhaust gas temperature and emission characteristic were measured simultaneously by using a testo 350 flue gas analyzer.According to the results,biodiesel fuels showed a higher fuel consumption rate and exhaust gas temperature under an increase of engine speed.They also exhibited lower NOx emission with a slight rise in CO and CO2 emission compared to mineral diesel fuel.ROME exhibited low emission gas compared to ROEE and mineral diesel.It can be evaluated as a promising alternative fuel for diesel engine.

Rosin side chain type catalyst-free vitrimers with high cross-link density,mechanical strength,and thermal stability

The emergence of vitrimer,a new class of polymer materials can address the problem of recyclability,reprocess ability and recyclability of thermosetting plastics.Rosin,a natural product,is an ideal raw material for the preparation of polymers in a more sustainable way.Nevertheless,due to the huge steric hindrance caused by the hydrogenated phenanthrene ring structure,the cross-link density of materials is frequently lowered.In this study,hydrogenated rosin was adopted for preparing hydrogenated rosin side-chain type diacids,which were reacted with mixed epoxy to obtain rosin side-chain type vitrimers.It was completely characterized by differential scanning calorimetry test,thermogravimetric analysis,shape memory test and self-healing test.The prepared vitrimers exhibited good self-healing properties,excellent heat resistance(T_(d)=352℃)as well as high mechanical properties(tensile strength of 46.75 MPa).The tricyclic diterpene structure of rosin was introduced into the side chain in order to avoid the reduction of cross-link density resulting from the huge steric hindrance of the rigid tricyclic hydrophenylene skeleton.Vitrimers can undergo dynamic transesterification reaction without external catalysts due to the autocatalytic effect of tertiary amines from epoxy.Moreover,our work expanded the application field of rosin,increased the added value of rosin,and provided a novel method for preparing rosin-based vitrimers with ideal properties.

Magnesium single-atom catalysts with superbasicity

Magnesium-related solid bases have long been considered catalysts with weak or medium basicity.Here we report the fabrication of Mg single-atom catalysts with superbasicity for the first time.A sublimation-migration-anchoring strategy is employed,in which the Mg net is sublimated,transported by Ar,and trapped by defective graphene(producing Mg_(1)/G).Simulated and experimental results demonstrate that Mg single atoms are anchored on graphene in tetra-coordination,and Mg single atoms cooperating with C atoms give superbasicity,which differs from conventional alkali/alkaline earth metal oxides with basicity originating from O atoms.This new solid base is highly active in the synthesis of dimethyl carbonate through transesterification of ethylene carbonate with methanol,which is usually catalyzed by strong bases.The turnover frequency value reaches 99.6 h^(-1) on Mg_(1)/G,which is much higher than that of traditional Mg-related counterparts(1.0–5.6 h^(-1))and even superior to that of typical Na and K-related solid superbases(29.8–36.2 h^(-1))under similar conditions.

形状记忆聚己内酯/氧化钨纳米线复合薄膜的光导二维到三维变形结构

形状记忆材料在受到外部刺激时具备可编程的复杂形状和大变形,该特性对其潜在应用至关重要.通常情况下将平面二维结构转化为复杂三维结构需要设计非对称的或双层薄膜结构.在本工作中,我们提出了一个简单的策略以实现二维到三维结构的转变,即可以通过激光刺激预拉伸复合薄膜的特定点进而变形成各种预先确定的形状序列.具体的,将吸光性W18O49纳米线物理掺杂到丙烯酸封端的聚己内酯交联网络中,当用98 mW cm^(−2)的激光刺激复合薄膜时,温度梯度和单层薄膜在厚度维度上的单畴取向导致形状记忆聚己内酯/W_(18)O_(49)纳米线复合薄膜的面外弯曲变形.紧接着,通过调控激光辐照时间、薄膜厚度和预拉伸应变,可以实现复合薄膜的不同弯曲变形速率和弯曲幅度.此外,通过将预拉伸的平面二维状聚合物薄膜与剪纸技术相结合,复合薄膜在受激后可以朝着更为复杂的三维形状发生变化.通过激活同一薄膜内的动态酯交换反应也可以实现聚己内酯基复合薄膜的二维到三维形状转化.因此这种新型薄膜在生物医学器件或软机器人领域具有巨大的应用潜力.

Rational fabrication of ordered porous solid strong bases by utilizing the inherent reducibility of metal-organic frameworks

Ordered porous solid strong bases(OPSSBs)have attracted great research interest due to the excellent performance as heterogeneous catalysts in various reactions.The main obstacle for fabricating OPSSBs is the requirement of high temperature to produce strong basicity on ordered porous materials.For example,the temperatures of 600-650℃ are required for the decomposition of base precursor NaNO_(3)to basic sites on mesoporous silica SBA-15 and zeolite Y.Such high decomposition temperatures are energy-intensive and harmful to the structure of supports.Herein,we report the fabrication of OPSSBs by utilizing the redox interaction between base precursor and low-valence metal centers(e.g.,Cr^(3+))in metal-organic frameworks(MOFs).The base precursor NaNO_(3)on MIL-101(Cr)can be converted to basic sites entirely at 300℃,which is quite lower than those of the conventional thermal conversion on SBA-15 and zeolite Y(600-650℃).The exploration on decomposition mechanism reveals that the valence change of Cr^(3+)to Cr^(6+)takes place during the conversion of NaNO_(3)to basic sites.In this way,MOFs-derived base catalysts have been synthesized successfully by the host-guest redox strategy and exhibit high catalytic activity in typical base-catalyzed reactions.

Development of solid base catalyst X/Y/MgO/-Al_(2)O_(3) for optimization of preparation of biodiesel from Jatropha curcas L.seed oil

The preparation and regeneration conditions of the identified catalyst X/Y/MgO/?-Al2O3 with high catalytic activity were studied and optimized. The biodiesel was prepared by transesterification of Jatropha curcas seed oil produced in Guizhou with methanol at its reflux temoerature in the presence of X/Y/MgO/?-Al2O3 . The pilot plant tests were carried out in a 100 L reaction vessel. Both average yield and fatty acid methyl esters (FAME) content reached more than 96.50% under the optimum reaction conditions of the pilot plant tests designed with an oil/methanol molar ratio of 1 : 10, catalyst concentration of 1.00%, and reaction time of 3 h at reflux temperature. In addition, analysis shows that the quality of biodiesel meets the standard EN 14214.